1. Field of the Invention
The present invention relates to, for example, a transistor, a semiconductor device, and manufacturing methods thereof. The present invention relates to, for example, a display device, a light-emitting device, a lighting device, a power storage device, a storage device, an imaging device, a processor, and an electronic device. The present invention relates to a method for manufacturing a display device, a liquid crystal display device, a light-emitting device, a storage device, an imaging device, and an electronic device. The present invention relates to a driving method of a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a storage device, and an electronic device.
Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. In addition, one embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter.
In this specification and the like, a semiconductor device generally means a device that can function by utilizing semiconductor characteristics. A storage device, a display device, a light-emitting device, a lighting device, an electro-optical device, a semiconductor circuit, and an electronic device include a semiconductor device in some cases.
2. Description of the Related Art
In recent years, a transistor including an oxide semiconductor has attracted attention. Patent Document 1 discloses an example in which a transistor including an oxide semiconductor in a channel formation region (hereinafter referred to as an oxide semiconductor transistor) is used in a dynamic random access memory (DRAM). The oxide semiconductor transistor has extremely low leakage current (also referred to as off-state current) in an off state; thus, a low-power DRAM having a low refresh frequency can be formed.
In Patent Document 2, a nonvolatile memory including an oxide semiconductor transistor is disclosed. Unlike a flash memory, the nonvolatile memory has unlimited cycling capability, consumes less power, and can easily operate at high speed.
Patent Document 2 discloses an example in which an oxide semiconductor transistor has a second gate to control the threshold voltage of the transistor so that the off-state current of the transistor is lowered.
Patent Documents 2 and 3 each disclose a structure example of a circuit for driving the second gate.